<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
		<style></style>
		<script src="js/4-23-js-1.js" language="javascript"></script>
	</head>
	<body>
		<input type="button" value="click" id="btn1"/>
		<input type="button" value="click" id="btn2"/>
		<!-- <script language="javascript">
			document.write("hello world")
		</script> -->
		
		<button id="btn3">click</button>
		<button>click</button>
	</body>
</html>